The present invention relates to a method for fabricating an optical conductor which can be used for optically interconnecting electronic and/or photonic equipment. The present invention is particularly suitable for making a waveguide element that comprises an optically transmissive rod and at least one reflective surface which is inclined, respectively, relative to an external planar surface and the longitudinal axis of the rod.
The increasingly high transmission rates typical of present-day computer and telecommunications equipment have led to the use of optical conductors, also called waveguides, as the main conduits for data which may be transmitted at rates of a gigabit and more per second. In telecommunications equipment, waveguides have been used to interconnect circuit cards which are mounted perpendicularly to a backplane of the equipment. The optical interconnections provided by waveguides in such equipment have heretofore employed several optical fibers which extend from a light source to respective receivers. Alternatively, a single optical fiber has been coupled to the light source, and tappings have been made by splicing optical fibers at intervals along its length. The tappings convey light to the receivers.
As the number and complexity of the interconnections to be made by optical tappings increases, the difficulties encountered in producing and installing a waveguide that is based on optical fibers likewise multiply. Moreover, there is the problem of protecting such waveguides from physical defects which affect optical properties. Although it is convenient to make a waveguide of light-transmissive plastic, and while a bare plastic waveguide is functional, it has been deemed preferable to coat such a waveguide so as to reduce scratching and contamination, both of which cause leakage of light at the surface of the waveguide. A coating of this sort must have a refractive index lower than that of the plastic to ensure confinement of light within the waveguide.
If the coating were of plastic, applied by solution-coating, difficulties could be encountered from the solvent's attacking the plastic material of the waveguide. If electrostatic coating were used, with subsequent baking to fuse the plastic coating, that baking could cause distortion of the waveguide, with consequent disturbance of the optical path.